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Selection of hard spring and winter wheat with no polyphenol oxidase activity
S. M. HYSTAD (1). (1) Montana State University, Bozeman, MT, U.S.A.
Wheat (<i>Triticum aestivum</i>) polyphenol oxidase (PPO) contributes significantly to the time dependent discoloration of Asian noodles and other food products. Wheat contains multiple paralogous PPO genes expressed in seeds. To date, wheat noodle color improvement efforts have focused on breeding cultivars containing <i>PPO-D1</i> and <i>PPO-A1</i> alleles conferring reduced PPO activity. A major impediment to wheat quality improvement efforts is a lack of known low PPO alleles at the <i>PPO-A2 </i>and <i>PPO-D2 </i>loci. The discovery of mutant forms of these two PPO genes is critical to further reduce PPO activity and improve noodle color stability. In this study, a very low PPO line, 07OR1074, derived from crossing PI 117635 and PI 134049 (Seaspray) was selected for study. We have found novel mutations in four seed expressed PPO genes in 07OR1074 relative to commonly grown spring and winter wheat cultivars. To examine the impact of each PPO mutation upon total PPO activity and noodle quality 07OR1074 was crossed with spring wheat cultivars Vida and Choteau. PPO activity was measured on F<sub>2:3</sub> plants grown under greenhouse conditions. Evaluation of progeny indicated there is a substantial genotypic effect on PPO activity with at least three of the four PPO genes contributing significantly to total PPO activity. The impact of each gene upon noodle quality is currently being assessed. The results are expected to show that mutations in each PPO gene are important to lowering overall wheat seed PPO activity to produce a more desirable and marketable product.
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